Zoho Api rejects leads with .cookie in the email address.

Zoho Api rejects leads with .cookie in the email address.

Why does the api not allow a lead with '.cookie' in the email? We have a user whose last name is cookie and when we try to sync the lead into zoho the request fails with 

"{\"response\":{\"error\":{\"message\""Unable to process your request. Please verify if the name and value is appropriate for the \\\"searchValue\\\" parameter.\",\"code\""4600\"}}}\n"


Both search and post requests to create fail for the email which is valid.